The present invention relates to a control system for controlling an electric motor fan of a vehicle such as a motor vehicle.
FIG. 5 shows one conventional fan control system for a passenger car (as disclosed in "NISSAN Shingatasha Kaisetsusho (new model maintenance manual)", Vol. U12-2, pages B-48 and B-95, Oct. 1989). This system includes a vehicle speed sensor 1, a temperature sensor 2 for sensing the temperature of an engine cooling water, an air conditioner switch SW1, and a control circuit 3 for controlling electric fan motors M1 and M2 for moving air toward a radiator of the engine coolant and a condenser of an air conditioning system, through motor relays Ry1 and Ry2.
When the vehicle is in motion, the radiator and condenser receive a flow of cool outside air due to the vehicle motion. Therefore, the control system stops the fan motors M1 and M2 when the vehicle speed is higher than 80 km/h and the engine cooling water temperature is lower than 105.degree. C., as shown in FIG. 6. When the vehicle speed is lower than 80 km/h and the water temperature is lower than 95.degree. C., this control system turns off the motors M1 and M2 if the air conditioner switch SW1 is off. When the air conditioner switch SW1 is on, a clutch for an air conditioning compressor is engaged, and the air conditioning system is in an operative state. Therefore, this control system runs the motors M1 and M2, regardless of the vehicle speed and the water temperature, when the air conditioning system is working.